1. Field
Embodiments of the present invention relate to a caliper disc brake, which improves a rollback performance of a piston.
2. Description of the Related Art
In general, braking apparatuses are used to decelerate or stop a vehicle during driving, or maintain a parked state of the vehicle, and perform a braking action by changing kinematic energy of the vehicle into heat energy using frictional force.
Each braking apparatus includes a unit to substantially perform the braking action, a braking energy supply unit, a manipulation unit, and a transmission unit.
Brakes are divided into main brakes, parking brakes, and sub-brakes according to purposes.
The main brakes are necessary to decelerate a velocity of a vehicle, or to quickly stop the vehicle according to circumstances. Most main brakes are foot-actuated brakes, which are actuated by a driver's foot, and manipulation power of a driver, i.e., a pedal pressure, is changed into braking power of a vehicle wheel via an intermedium, such as oil pressure or air pressure.
Among hydraulic main brakes, a caliper disc brake, which has a brake disc made of cast iron and rotated together with a wheel instead of a drum, brakes a wheel using frictional force obtained by pushing brake pads operated by a hydraulic piston to both outer sides of the brake disc.
The caliper disc brake includes the brake disc, a caliper, disc pads, and the piston.
The caliper includes a hydraulic pipe, to which oil pressure generated from a master brake unit by manipulation of a brake pedal is transmitted, the disc pads compressed onto both side surfaces of the brake disc by pressure of the piston, installed in the caliper and rectilinearly moving by the oil pressure, to produce friction with the brake disc so as to brake the wheel, and a piston return seal installed at the cylinder to return the piston to its former position and prevent leakage of a brake oil.
If elasticity of the conventional piston return seal is weakened, return of the piston is difficult and the disc pads are still compressed onto the brake disc even if no braking motion is carried out, and thus the brake is in an operating state at any time.